1. Technical Field of the Invention
The present invention relates generally to an optical fiber fluorosensor and more particularly to an improved fluorosensor having an active core for determining the concentration of a chemical species.
2. Related Art
Active optical fiber sensors have been developed for determining the concentration of a particular analyte or chemical species. The sensors basically fall into three groups--sensors having an active fluorescent cladding, sensors having an active fluorescent core, and sensors having both an active cladding and core. It is desirable to maximize the power efficiency of such a fiber sensor, as discussed in NASA Contractor Report 4333, "Injection Efficiency of Bound Modes", by Claudio Oliveira Egalon, Contract NAS1-18347, Nov. 1990. This report observes the power efficiency P.sub.eff of active cladding optical fibers, wherein a is the core radius and k=2.pi./.lambda., wherein .lambda. is the wavelength of the light emitted by the cladding sources. See pp. 80-82. As ka was increased by varying the core radius a, a decrease in power efficiency was observed in a bulk distribution of cladding sources and an increase was observed in a thin film distribution. See p. 110 and FIGS. IV-10 and IV-11. Similar relationships were found when .lambda. was varied. See p. 101 and FIG. IV-6(b). There was no consideration of the effect of varying ka of an active core optical fiber.